Refrigeration



April 10, 1956 c. E. PLOEGER 2,741,424

REFRIGERATION Filed June 22, 1951 &

g Fa i7 325; w 3 7 44 I N r 57 Iii ii L7; 59 F5 5;? =3 4/ J) a f f/ I NV EN TOR. 415 4/ QJWM659 BY $9 a 5 2,741,424 Patented Apr. 10, 1955nnFIuGERAnoN Clyde Edward Ploeger, Evansville, Ind, assignor to'Servel,Inc., New York, N. Y., a corporation of Eelaware Application June 22,15L Serial No. 233,908

3 Claims. (Cl. 239-206) This invention relates to refrigeration andparticularly to means for preventing slugs of oil or liquid refrigerantfrom entering the cylinders of a refrigerant compressor.

In hermetically sealed motor compressor units, wherein the suction gasenters the compressor through the motor compartment, or wherein thesuction gas line is connected to the motor compartment, the problem ofoil slugging is one of considerable importance.

In this type of unit, during shutdown periods, refrigerant vapor maycondense in the crankcase of the compressor and in the motorcompartment, thereby raising the oil level in these parts considerablyhigher than normally intended. Then, when the compressor is started, theentrained liquid refrigerant may cause violent boiling in the oil. Thisboiling may be to such an extent that the mixture may even foam up andenter the inlet ports of the cylinder as solid liquid. When this occurs,the cylinder is filled with liquid refrigerant and oil in amounts suchthat severe hammering occurs which may in turn break the suction valvesand the connecting rods, or otherwise damage the compressor; unlesssteps are taken to throttle the passage ofthis liquid so that the liquidrefrigerant and oil is fed to the cylinders in small amounts.

The present invention contemplates a device for protecting the valvesand other moving parts of a refrigerant compressor by throttling thepassage of liquid refrigerant and oil to the cylinders each time thecompressor is started.

Specifically, I provide a check valve in the suction chamber leading tothe intake manifold of the compressor. One end of this suction chamberis in open communication with the crankcase and with the motorcompartment. The opposite end of this suction chamber is incommunication, through the check valve, with the intake manifold of thecompressor. The valve is provided with two sets of ports for parallelflow of refrigerant vapor to the intake manifold and when the compressoris operating normally, that is, when only relatively dry refrigerantvapor is flowing thereto, both sets of ports are open. However, when oiland liquid refrigerant in sufficient concentration try to pass throughthe ports, this relatively dense oil and vapor mixture causes the valveto close one set of ports, thus restricting the flow to the other set ofports. The amount of oil and vapor mixture that is permitted to passthrough the single set of ports is not sufficient to damage thecompressor valves or other moving parts. As soon as this liquidrefrigerant is removed from the oil in the crankcase by evaporation, thevalve resumes its normal position and dry refrigerant gas again flowsthrough both sets of ports to the intake manifold.

The invention, together with the above and other objects and advantages,will be more fully understood by reference to the following descriptiontaken in connection with the accompanying drawings, wherein:

Fig. 1 is a longitudinal section of a portion of a motor compressor unitincorporating my invention;

Fig. 2 is a vertical section through my improved check valve, showingthe valve in open position; and

Fig. 3 is a section similar to Fig. 2 but taken at an angle of theretoand showing the valve in closed position.

Referring to the drawing, an hermetically sealed casing 10 encloses amotor compressor unit adapted for use in a refrigerating system. Only somuch of the unit as is necessary for complete understanding of theinvention is illustrated in the drawing. As shown, an electric inductionmotor comprising a stator 11 and a rotor 12 having an air gap 13therebetween is arranged within the casing 16. The stator may be securedwithin the casing in any suitable manner as by a'shrink fit. The casingis provided with a removable head 15 having an opening 16 therein, whichopening is connected by a suitable conduit, not shown, to the suctionside of the expander or evaporator of the refrigerating system in whichthe unit is connected. A fine mesh strainer 17 is located at the outletof the opening 16.

The compressor includes a crankshaft 18 attached to the rotor 12 andjournaled at one end in a support 19. The opposite end of the crankshaftis supported in a suitable manner, not shown, within the opposite end ofthe casing 10. The compressor is of the multiple cylinder type, only onesuch cylinder, 20, being shown and described. A piston 21 is arrangedwithin the cylinder 29 and is connected to the crankshaft 18 by aconnecting rod 22. The casing 10 is formed with a suction chamber 23opening at one end into a motor compartment 24'. The motor compartmentis in open communication with a crankcase 25 by means of openings 26provided in the upper portion of the support 19. A passageway 27 leadsfrom the suction chamber 23 into an intake manifold 28. A port 29provided with a suction valve 39 leads from the intake manifold into thecylinder 20 and an exhaust port 31 provided with an exhaust valve 32leads. from the cylinder 2% to an exhaust manifold 33. The exhaustmanifold is connected by a suitable conduit, not shown, to the condenserof the refrigerating system in which the motor compressor unit is used.So, as to provide for how of oil and liquid refrigerant between themotor compartment 24 and the crankcase 25, the stator 11 is providedwith an opening 11 in the lower portion thereof and the support 19 isprovided with an opening 19 in its lower portion. The above describedcompressor isof a more or less conventional type and. is merely oneillustration of a type of compressor in which my invention may beincorporated.

In accordance with my invention, the passageway 27 that leads from thesuction chamber 23 into the intake manifold 28 is provided with a checkvalve, indicated generally by reference numeral 34. This check valveincludes a tube 35 provided with a flange 36 adapted to fit within anotch 37 in the casing 10 for holding the tube in position. The tube 35is provided with two sets of ports or openings 38 and 39. As shown, theports 38 are much larger than the ports 39. Within the tube 35, andbetween the ports 38 and 39, a valve seat 40 is formed. A buoyant checkball 41 is located within the tube 35 and is retained therein by flangedportions 42 at the lower end of the tube. A compression spring 43,having its lower end in contact with the check ball 41 and its upper endin contact with a retaining pin 44, urges the check ball away from thevalve seat 40 and toward the lower end of the tube 35.

In operation, assuming that the suction line of a refrigerating systemis connected to the inlet opening 16 leading to the motor compartment 24and that the exhaust manifold 33 is connected to the condenser of suchrefrigerating system, refrigerant gas is drawn from the suction lineinto the motor compartment, through the gap 13 between the stator androtor and into the suction chamber 23.

Assuming also that the compressor has been running for a period of timesuch that the refrigerant gas drawn into the suction chamber 23 isrelatively dry, under these conditions of operation, the check ball 41will be in the lower portion of the tube 35 and refrigerant gas willpass from the suction chamber 23 throughboth sets of ports Assuming nowthat the compressor has been standing idle for a period of time and thatrefrigerant vapor has condensed and collected. in the crankcase 25 andin the motor compartment 24, under these conditions, when the compressoris later put in operation, the liquid refrige'rant collected in thecrankcase and in the motor compartment may cause violent boiling in theoil and foam may enter the suction chamber 23 and flow into the valvetube 35. However, duclto the fact that the a density of this oil andrefrigerant foam is much greater than that of dry refrigerant gas, thecheck ball'41 will be buoyed or lifted from the lower end of the tubeand moved into engagement with the valve seat 49, thereby cutting offthe flow of the mixture of oil and refrigerant vapor through the ports38. With the check valve closed, oil and liquid refrigerant, in amountstoo small to cause damage to the compressor, will continue to flowthrough the ports 39. After a short period of time all of the liquidrefrigerant in the crankcase and in the motor compartment will haveevaporated, foaming will stop and only relatively dry refrigerant gaswill pass from the suction chamber 23, through the check valve 34 andinto the intake manifold 28. Then the spring 43 V will move the checkball 41 away from the valve seat and into the lower part of the tube 35and the refrigerant gas will again pass from the suction chamber 23through both sets of ports 38 and 39 into the intake manifold 28.

Although but one specific form of my invention has been illustrated anddescribed and this specific form has been incorporated in a motorcompressor unit of a refrigerating system of thecompressor-condenser-expander type, my invention obviously may takeother forms and be variously applied; 7 The invention is thereforelimited only as defined in the claims.

I claim:

1. A compressor having a crankcase containing a quantity of oil and attimes a quantity of liquid refrigerant, said compressor including acylinder, a piston within said cylinder, means for reciprocating saidpiston,

inlet and outlet valves leading to and from said cylinder, means formingsuction'and exhaust chambers connected to and leading to and from saidcylinder, said suction chamber also beingin open communication with saidcrankcase for flow of refrigerant vapor and entrained oil from thecrankcase to said cylinder, and means insaid suction chamber operableresponsive to the density of the mixture of refrigerant vapor and oilpassing therethrough for automatically throttling the flow of suchfluid.

2.- A compressor'having a crankcase containing a quantity of oil and attimes containing a quantity of liquid refrigerant, 'said compressorincluding a cylinder, a piston within said cylinder, means forreciprocating said piston, inlet and outlet valves leading to and fromsaid cylinder, means forming suction and exhaust cham bers connected toand leading to and from said cylinder,

said suction chamber also being in open communication with saidcrankcase for flow of refrigerant vapor and entrained oil from thecrankcase to said cylinder, jmeans in said suction chamber providingparallel paths of flow of vfluid between said crankcaseand saidcylinder, and means in at least one of said paths of flow operableresponsive to the density of fluid flowing through said suction chamberfor throttling the flow of fluid to said cylinder.

3. A compressor having a crankcase containing a quantity of oil and attimes containing a quantity of liquid refrigerant, said compressorincluding a cylinder, a piston Within said cylinder, means forreciprocating said piston, inlet and outlet valves leading to and fromsaid cylinder, means forming suction and exhaust chambers connected toand leading to and from said cylinder, said suction chamber also beingin open communication with said crankcase for flow ofrefrigerant vaporand entrained oil from the crankcase to the cylinder, a valve in saidsuction chamber, said valve having a plurality of ports, and means forclosing certain of said' ports while leaving others of said ports open,said last named means being operable responsive to the density of fluidpassing through said valve.

References Cited in the file of this patent UNITED STATES VPATENTS' a wm-

